Salicylaldimine ligands, such as 5-nitro-N(2,6-diisopropylphenyl)salicylaldimine, 3,5-dinitro-N(2,6-diisopropylphenyl)salicylaldimine, and 3-phenyl-N(2,6-diisopropylphenyl) salicylaldimine were checked in the oxidative addition to bis(1,5-cyclooctadiene)nickel(0) to prepare, after activation by methylaluminoxane (MAO), novel nickel-based catalytic systems active in the polymerization of methyl methacrylate. The catalytic behavior of the aforementioned systems, in terms of activity, molecular weight, and polydispersity of the resulting poly(methyl methacrylate) as well as its stereoregularity degree, was investigated as a function of the Al/Ni molar ratio, reaction temperature, and nature of the salicylaldimine ligand. The effect of ethylene atmosphere present during the preparation of the catalyst precursors was also investigated. The results are discussed and compared with those previously obtained by bis(salicylaldiminate)nickel(II)MAO catalytic systems. (C) 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1716-1724, 2003.